Physical Resources: Air, Water, Soil, Air for Respiration Air for Combustion Contribution of Building to Normalize Temperature All over India Air, Water and Soil Pollution (Brief Introduction), Ozone Layer Holes and its Possible Bio-chemical Cycle, Water Oxygen, Carbon and Nitrogen

Explain briefly


Nitrogen cycle

In the atmosphere, the concentration of nitrogen is about 78%. It is essential for plants. Nitrogen forms a structural component of many important molecules such as DNA, RNA, and other vitamins.
Plants cannot absorb nitrogen from the atmosphere. Certain forms of bacteria are able to convert atmospheric nitrogen into usable forms such as nitrates and nitrites. Such nitrogen fixing bacteria are commonly found in the roots of legumes (plants of pulses) inside special structures called root nodules. These usable forms of nitrogen are absorbed by plants to produce many compounds such as amino acids, which in turn form proteins. When an animal feeds on plants, nitrogen enters its body.When plants and animals die, they start decomposing after some time. During this process, proteins are converted into nitrates and nitrites by the action of decomposing bacteria. Certain other forms of bacteria convert nitrates and nitrites into elemental nitrogen. Thus, nitrogen flows between the various components of the biosphere in a cyclical manner.
There are basically 5 steps of nitrogen cycle that help in fixing atmospheric nitrogen:
  • Nitrogen Fixation (N 2 to NO 3 - or NH 4 )
  • Nitrification (NH 3 to NO 3 - )
  • Assimiliation (here the NH 3 and NO 3 - are incorporated into the biological tissues)
  • Ammonification (organic nitrogen compounds to NH 3 )
  • Denitrification (NO 3 - to N 2 )
Carbon Cycle
Carbon enters life forms through the process of photosynthesis. Photosynthesis is the process by which plants prepare food in the presence of sunlight and chlorophyll. During photosynthesis, carbon dioxide and water combine to produce glucose and oxygen. This changes the atmospheric carbon into glucose molecules.
Glucose, which is a source of food, is utilized by organisms to produce energy during respiration. During this process, glucose is broken down in the presence of oxygen to produce carbon dioxide.
Thus, through the processes of photosynthesis and respiration, carbon is utilized and then returned to the environment.
All organisms do not need oxygen to break down glucose and produce energy. The organisms which survive in the absence of oxygen are called anaerobes.
Another process that releases carbon dioxide is called combustion. It is the process of burning. Many substances release carbon dioxide on burning. Vehicular emissions, industrial fumes, and the gases released during the process of cooking are some instances during which carbon dioxide is released.

Oxygen cycle

Oxygen is an important component of everyday life. We cannot survive without oxygen. It comprises about 21% of atmospheric air. It is a component of several biological molecules such as carbohydrates, proteins, nucleic acids, and fats.
Like carbon dioxide, oxygen too is cycled through the process of photosynthesis and respiration. Oxygen is also utilized during combustion or burning.

Steps of oxygen cycle.
Step 1)Animals take in oxygen through the process of respiration. And release CO2 into the atmosphere.
Step 2)Carbon dioxide, released by animals is used in plants in the process of photosynthesis.
Step 3)Plants release oxygen into the atmosphere as a by-product of photosynthesis.
step 4)Fuels need oxygen for combustion so they take oxygen and release CO2 into the atmosphere as a by product along with other gases like N2 etc.
step 5)CO2 is released into the air in the process of decaying of dead animals and plants.
step 6)This CO2 is taken by plants for the process of photosynthesis and O2 is released, and this process continues.

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